*{
    margin: 0;
    padding: 0;
}
body{
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #efeeee;
}
.container{
    width: 700px;
    height: 600px;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    align-items: center;
}
.container .item{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    width: 100px;
    margin: 30px;
}
/* 给盒子设置阴影，左上角白(页面背景前提是灰色)，右下角黑，并设置过渡效果 */
.container .item .img{
    width: 100px;
    height: 100px;
    box-shadow: 18px 18px 30px rgba(0, 0, 0, .1),-18px -18px 30px rgba(255, 255, 255, 1);
    border-radius: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #efeeee;
    transition: box-shadow .2s ease-out;
    position: relative;
    margin-bottom: 30px;
}
.container .item .img i{
    font-size: 50px;
    transition: font-size .2s ease-out;
}
.container .item p{
    color: slategray;
}
/* 鼠标滑过时收缩外阴影，设置内阴影(顺向黑，逆向白) */
.container .item .img:hover {
    box-shadow: 0 0 0 rgba(0, 0, 0, .1),0 0 0 rgba(255, 255, 255, 1),
    inset 18px 18px 30px rgba(0, 0, 0, .1),
    inset -18px -18px 30px rgba(255, 255, 255, 1);
    transition: box-shadow .2s ease-out;
}
.container .item .img:hover i{
    font-size: 40px;
    transition: font-size .2s ease-out;
}